x86/kprobes: Fix crash when probing CS CALL instructionsgrafted

When using eBPF to probe CS CALL instructions within a function,
a crash can be triggered.

The eBPF tool probes offset 257 of the __hrtimer_run_queues()
function:

<__hrtimer_run_queues+249>:  nopl   0x0(%rax,%rax,1)
<__hrtimer_run_queues+254>:  mov    %r14,%rdi
<__hrtimer_run_queues+257>:  cs call <__x86_indirect_thunk_r12>
<__hrtimer_run_queues+263>:  mov    %eax,%r12d
<__hrtimer_run_queues+266>:  xchg   %ax,%ax
<__hrtimer_run_queues+268>:  mov    %r13,%rdi

Which triggers this crash:

  BUG: unable to handle page fault for address: 00000000000f41c9
  #PF: supervisor write access in kernel mode
  #PF: error_code(0x0002) - not-present page
  PGD 0 P4D 0
  Oops: 0002 [#1] SMP NOPTI
  CPU: 1 PID: 0 Comm: swapper/1 Kdump: loaded Tainted: P
  RIP: 0010:__hrtimer_run_queues+0x106/0x230

Note that __hrtimer_run_queues+0x106 is __hrtimer_run_queues+262, which is
at the 6th byte of the above CS CALL instruction. Since the CS CALL
instruction occupies 6 bytes, the exception occurred in the middle of that
call instruction.

The root cause is that when using eBPF tools to probe in the middle of a
function, a kprobe with INT3 is used as the underlying implementation.

During single-step emulation of the original CALL instruction,
int3_emulate_call() assumes that the probed CALL instruction is 5 bytes
long. However, the actual CS-prefixed CALL instruction occupies 6 bytes,
so it constructs an incorrect exception return address. When the CPU
returns from the kprobe handler, the next instruction to be executed is at
the address of the last byte of that CS CALL instruction. Coincidentally,
starting from that address, the CPU fetches and decodes a completely
different instruction, which ultimately triggers a kernel crash.

Fix the issue by using the actual instruction length obtained from
the instruction decoder when constructing the exception return
address, rather than relying on the hardcoded CALL_INSN_SIZE macro.

[ mingo: Refined the changelog ]

Fixes: 6256e668b7af ("x86/kprobes: Use int3 instead of debug trap for single-step")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Jinke Han <jinkehan@didiglobal.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Yafang Shao <laoar.shao@gmail.com>
Acked-by: Borislav Petkov <bp@alien8.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://patch.msgid.link/20260908073742.GA10517@didi-ThinkCentre-M920t-N000

1 files changed, 503 insertions, 0 deletions

diff --git a/fs/hfs/super.c b/fs/hfs/super.c
new file mode 100644
index 000000000..5e6d66ff4
--- /dev/null
+++ b/fs/hfs/super.c
@@ -0,0 +1,503 @@
+/*
+ *  linux/fs/hfs/super.c
+ *
+ * Copyright (C) 1995-1997  Paul H. Hargrove
+ * (C) 2003 Ardis Technologies <roman@ardistech.com>
+ * This file may be distributed under the terms of the GNU General Public License.
+ *
+ * This file contains hfs_read_super(), some of the super_ops and
+ * init_hfs_fs() and exit_hfs_fs().  The remaining super_ops are in
+ * inode.c since they deal with inodes.
+ *
+ * Based on the minix file system code, (C) 1991, 1992 by Linus Torvalds
+ */
+
+#include <linux/module.h>
+#include <linux/blkdev.h>
+#include <linux/backing-dev.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include <linux/mount.h>
+#include <linux/init.h>
+#include <linux/nls.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/vfs.h>
+
+#include "hfs_fs.h"
+#include "btree.h"
+
+static struct kmem_cache *hfs_inode_cachep;
+
+MODULE_DESCRIPTION("Apple Macintosh file system support");
+MODULE_LICENSE("GPL");
+
+static int hfs_sync_fs(struct super_block *sb, int wait)
+{
+	int ret;
+
+	mutex_lock(&HFS_SB(sb)->mdb_lock);
+	is_hfs_cnid_counts_valid(sb);
+	ret = hfs_mdb_commit(sb);
+	mutex_unlock(&HFS_SB(sb)->mdb_lock);
+
+	return ret;
+}
+
+/*
+ * hfs_put_super()
+ *
+ * This is the put_super() entry in the super_operations structure for
+ * HFS filesystems.  The purpose is to release the resources
+ * associated with the superblock sb.
+ */
+static void hfs_put_super(struct super_block *sb)
+{
+	cancel_delayed_work_sync(&HFS_SB(sb)->mdb_work);
+	hfs_mdb_close(sb);
+	/* release the MDB's resources */
+	hfs_mdb_put(sb);
+}
+
+static void flush_mdb(struct work_struct *work)
+{
+	struct hfs_sb_info *sbi;
+	struct super_block *sb;
+
+	sbi = container_of(work, struct hfs_sb_info, mdb_work.work);
+	sb = sbi->sb;
+
+	spin_lock(&sbi->work_lock);
+	sbi->work_queued = 0;
+	spin_unlock(&sbi->work_lock);
+
+	mutex_lock(&sbi->mdb_lock);
+	is_hfs_cnid_counts_valid(sb);
+	hfs_mdb_commit(sb);
+	mutex_unlock(&sbi->mdb_lock);
+}
+
+void hfs_mark_mdb_dirty(struct super_block *sb)
+{
+	struct hfs_sb_info *sbi = HFS_SB(sb);
+	unsigned long delay;
+
+	if (sb_rdonly(sb))
+		return;
+
+	spin_lock(&sbi->work_lock);
+	if (!sbi->work_queued) {
+		delay = msecs_to_jiffies(dirty_writeback_interval * 10);
+		queue_delayed_work(system_dfl_long_wq, &sbi->mdb_work, delay);
+		sbi->work_queued = 1;
+	}
+	spin_unlock(&sbi->work_lock);
+}
+
+/*
+ * hfs_statfs()
+ *
+ * This is the statfs() entry in the super_operations structure for
+ * HFS filesystems.  The purpose is to return various data about the
+ * filesystem.
+ *
+ * changed f_files/f_ffree to reflect the fs_ablock/free_ablocks.
+ */
+static int hfs_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+	struct super_block *sb = dentry->d_sb;
+	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
+
+	buf->f_type = HFS_SUPER_MAGIC;
+	buf->f_bsize = sb->s_blocksize;
+	buf->f_blocks = (u32)HFS_SB(sb)->fs_ablocks * HFS_SB(sb)->fs_div;
+	buf->f_bfree = (u32)HFS_SB(sb)->free_ablocks * HFS_SB(sb)->fs_div;
+	buf->f_bavail = buf->f_bfree;
+	buf->f_files = HFS_SB(sb)->fs_ablocks;
+	buf->f_ffree = HFS_SB(sb)->free_ablocks;
+	buf->f_fsid = u64_to_fsid(id);
+	buf->f_namelen = HFS_NAMELEN;
+
+	return 0;
+}
+
+static int hfs_reconfigure(struct fs_context *fc)
+{
+	struct super_block *sb = fc->root->d_sb;
+
+	sync_filesystem(sb);
+	fc->sb_flags |= SB_NODIRATIME;
+	if ((bool)(fc->sb_flags & SB_RDONLY) == sb_rdonly(sb))
+		return 0;
+
+	if (!(fc->sb_flags & SB_RDONLY)) {
+		if (!(HFS_SB(sb)->mdb->drAtrb & cpu_to_be16(HFS_SB_ATTRIB_UNMNT))) {
+			pr_warn("filesystem was not cleanly unmounted, running fsck.hfs is recommended.  leaving read-only.\n");
+			sb->s_flags |= SB_RDONLY;
+			fc->sb_flags |= SB_RDONLY;
+		} else if (HFS_SB(sb)->mdb->drAtrb & cpu_to_be16(HFS_SB_ATTRIB_SLOCK)) {
+			pr_warn("filesystem is marked locked, leaving read-only.\n");
+			sb->s_flags |= SB_RDONLY;
+			fc->sb_flags |= SB_RDONLY;
+		}
+	}
+	return 0;
+}
+
+static int hfs_show_options(struct seq_file *seq, struct dentry *root)
+{
+	struct hfs_sb_info *sbi = HFS_SB(root->d_sb);
+
+	if (sbi->s_creator != cpu_to_be32(0x3f3f3f3f))
+		seq_show_option_n(seq, "creator", (char *)&sbi->s_creator, 4);
+	if (sbi->s_type != cpu_to_be32(0x3f3f3f3f))
+		seq_show_option_n(seq, "type", (char *)&sbi->s_type, 4);
+	seq_printf(seq, ",uid=%u,gid=%u",
+			from_kuid_munged(&init_user_ns, sbi->s_uid),
+			from_kgid_munged(&init_user_ns, sbi->s_gid));
+	if (sbi->s_file_umask != 0133)
+		seq_printf(seq, ",file_umask=%o", sbi->s_file_umask);
+	if (sbi->s_dir_umask != 0022)
+		seq_printf(seq, ",dir_umask=%o", sbi->s_dir_umask);
+	if (sbi->part >= 0)
+		seq_printf(seq, ",part=%u", sbi->part);
+	if (sbi->session >= 0)
+		seq_printf(seq, ",session=%u", sbi->session);
+	if (sbi->nls_disk)
+		seq_printf(seq, ",codepage=%s", sbi->nls_disk->charset);
+	if (sbi->nls_io)
+		seq_printf(seq, ",iocharset=%s", sbi->nls_io->charset);
+	if (sbi->s_quiet)
+		seq_printf(seq, ",quiet");
+	return 0;
+}
+
+static struct inode *hfs_alloc_inode(struct super_block *sb)
+{
+	struct hfs_inode_info *i;
+
+	i = alloc_inode_sb(sb, hfs_inode_cachep, GFP_KERNEL);
+	return i ? &i->vfs_inode : NULL;
+}
+
+static void hfs_free_inode(struct inode *inode)
+{
+	kmem_cache_free(hfs_inode_cachep, HFS_I(inode));
+}
+
+static const struct super_operations hfs_super_operations = {
+	.alloc_inode	= hfs_alloc_inode,
+	.free_inode	= hfs_free_inode,
+	.write_inode	= hfs_write_inode,
+	.evict_inode	= hfs_evict_inode,
+	.put_super	= hfs_put_super,
+	.sync_fs	= hfs_sync_fs,
+	.statfs		= hfs_statfs,
+	.show_options	= hfs_show_options,
+};
+
+enum {
+	opt_uid, opt_gid, opt_umask, opt_file_umask, opt_dir_umask,
+	opt_part, opt_session, opt_type, opt_creator, opt_quiet,
+	opt_codepage, opt_iocharset,
+};
+
+static const struct fs_parameter_spec hfs_param_spec[] = {
+	fsparam_u32	("uid",		opt_uid),
+	fsparam_u32	("gid",		opt_gid),
+	fsparam_u32oct	("umask",	opt_umask),
+	fsparam_u32oct	("file_umask",	opt_file_umask),
+	fsparam_u32oct	("dir_umask",	opt_dir_umask),
+	fsparam_u32	("part",	opt_part),
+	fsparam_u32	("session",	opt_session),
+	fsparam_string	("type",	opt_type),
+	fsparam_string	("creator",	opt_creator),
+	fsparam_flag	("quiet",	opt_quiet),
+	fsparam_string	("codepage",	opt_codepage),
+	fsparam_string	("iocharset",	opt_iocharset),
+	{}
+};
+
+/*
+ * hfs_parse_param()
+ *
+ * This function is called by the vfs to parse the mount options.
+ */
+static int hfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
+{
+	struct hfs_sb_info *hsb = fc->s_fs_info;
+	struct fs_parse_result result;
+	int opt;
+
+	/* hfs does not honor any fs-specific options on remount */
+	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE)
+		return 0;
+
+	opt = fs_parse(fc, hfs_param_spec, param, &result);
+	if (opt < 0)
+		return opt;
+
+	switch (opt) {
+	case opt_uid:
+		hsb->s_uid = result.uid;
+		break;
+	case opt_gid:
+		hsb->s_gid = result.gid;
+		break;
+	case opt_umask:
+		hsb->s_file_umask = (umode_t)result.uint_32;
+		hsb->s_dir_umask = (umode_t)result.uint_32;
+		break;
+	case opt_file_umask:
+		hsb->s_file_umask = (umode_t)result.uint_32;
+		break;
+	case opt_dir_umask:
+		hsb->s_dir_umask = (umode_t)result.uint_32;
+		break;
+	case opt_part:
+		hsb->part = result.uint_32;
+		break;
+	case opt_session:
+		hsb->session = result.uint_32;
+		break;
+	case opt_type:
+		if (strlen(param->string) != 4) {
+			pr_err("type requires a 4 character value\n");
+			return -EINVAL;
+		}
+		memcpy(&hsb->s_type, param->string, 4);
+		break;
+	case opt_creator:
+		if (strlen(param->string) != 4) {
+			pr_err("creator requires a 4 character value\n");
+			return -EINVAL;
+		}
+		memcpy(&hsb->s_creator, param->string, 4);
+		break;
+	case opt_quiet:
+		hsb->s_quiet = 1;
+		break;
+	case opt_codepage:
+		if (hsb->nls_disk) {
+			pr_err("unable to change codepage\n");
+			return -EINVAL;
+		}
+		hsb->nls_disk = load_nls(param->string);
+		if (!hsb->nls_disk) {
+			pr_err("unable to load codepage \"%s\"\n",
+					param->string);
+			return -EINVAL;
+		}
+		break;
+	case opt_iocharset:
+		if (hsb->nls_io) {
+			pr_err("unable to change iocharset\n");
+			return -EINVAL;
+		}
+		hsb->nls_io = load_nls(param->string);
+		if (!hsb->nls_io) {
+			pr_err("unable to load iocharset \"%s\"\n",
+					param->string);
+			return -EINVAL;
+		}
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+/*
+ * hfs_read_super()
+ *
+ * This is the function that is responsible for mounting an HFS
+ * filesystem.	It performs all the tasks necessary to get enough data
+ * from the disk to read the root inode.  This includes parsing the
+ * mount options, dealing with Macintosh partitions, reading the
+ * superblock and the allocation bitmap blocks, calling
+ * hfs_btree_init() to get the necessary data about the extents and
+ * catalog B-trees and, finally, reading the root inode into memory.
+ */
+static int hfs_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+	struct hfs_sb_info *sbi = HFS_SB(sb);
+	struct hfs_find_data fd;
+	hfs_cat_rec rec;
+	struct inode *root_inode;
+	int silent = fc->sb_flags & SB_SILENT;
+	int res;
+
+	atomic64_set(&sbi->file_count, 0);
+	atomic64_set(&sbi->folder_count, 0);
+	atomic64_set(&sbi->next_id, 0);
+
+	/* load_nls_default does not fail */
+	if (sbi->nls_disk && !sbi->nls_io)
+		sbi->nls_io = load_nls_default();
+	sbi->s_dir_umask &= 0777;
+	sbi->s_file_umask &= 0577;
+
+	spin_lock_init(&sbi->work_lock);
+	INIT_DELAYED_WORK(&sbi->mdb_work, flush_mdb);
+
+	sbi->sb = sb;
+	sb->s_op = &hfs_super_operations;
+	sb->s_xattr = hfs_xattr_handlers;
+	sb->s_flags |= SB_NOATIME | SB_NODIRATIME;
+	mutex_init(&sbi->mdb_lock);
+	mutex_init(&sbi->bitmap_lock);
+
+	mutex_lock(&sbi->mdb_lock);
+	res = hfs_mdb_get(sb);
+	mutex_unlock(&sbi->mdb_lock);
+	if (res) {
+		if (!silent)
+			pr_warn("can't find a HFS filesystem on dev %s\n",
+				hfs_mdb_name(sb));
+		res = -EINVAL;
+		goto bail;
+	}
+
+	/* try to get the root inode */
+	res = hfs_find_init(HFS_SB(sb)->cat_tree, &fd);
+	if (res)
+		goto bail_no_root;
+	res = hfs_cat_find_brec(sb, HFS_ROOT_CNID, &fd);
+	if (!res) {
+		if (fd.entrylength != sizeof(rec.dir)) {
+			res =  -EIO;
+			goto bail_hfs_find;
+		}
+		hfs_bnode_read(fd.bnode, &rec, fd.entryoffset, fd.entrylength);
+		if (rec.type != HFS_CDR_DIR)
+			res = -EIO;
+	}
+	if (res)
+		goto bail_hfs_find;
+	res = -EINVAL;
+	root_inode = hfs_iget(sb, &fd.search_key->cat, &rec);
+	hfs_find_exit(&fd);
+	if (!root_inode)
+		goto bail_no_root;
+
+	if (is_bad_inode(root_inode)) {
+		iput(root_inode);
+		goto bail_no_root;
+	}
+
+	set_default_d_op(sb, &hfs_dentry_operations);
+	res = -ENOMEM;
+	sb->s_root = d_make_root(root_inode);
+	if (!sb->s_root)
+		goto bail_no_root;
+
+	/* everything's okay */
+	return 0;
+
+bail_hfs_find:
+	hfs_find_exit(&fd);
+bail_no_root:
+	pr_err("get root inode failed\n");
+bail:
+	hfs_mdb_put(sb);
+	return res;
+}
+
+static int hfs_get_tree(struct fs_context *fc)
+{
+	return get_tree_bdev(fc, hfs_fill_super);
+}
+
+static void hfs_free_fc(struct fs_context *fc)
+{
+	kfree(fc->s_fs_info);
+}
+
+static const struct fs_context_operations hfs_context_ops = {
+	.parse_param	= hfs_parse_param,
+	.get_tree	= hfs_get_tree,
+	.reconfigure	= hfs_reconfigure,
+	.free		= hfs_free_fc,
+};
+
+static int hfs_init_fs_context(struct fs_context *fc)
+{
+	struct hfs_sb_info *hsb;
+
+	hsb = kzalloc_obj(struct hfs_sb_info);
+	if (!hsb)
+		return -ENOMEM;
+
+	fc->s_fs_info = hsb;
+	fc->ops = &hfs_context_ops;
+
+	if (fc->purpose != FS_CONTEXT_FOR_RECONFIGURE) {
+		/* initialize options with defaults */
+		hsb->s_uid = current_uid();
+		hsb->s_gid = current_gid();
+		hsb->s_file_umask = 0133;
+		hsb->s_dir_umask = 0022;
+		hsb->s_type = cpu_to_be32(0x3f3f3f3f); /* == '????' */
+		hsb->s_creator = cpu_to_be32(0x3f3f3f3f); /* == '????' */
+		hsb->s_quiet = 0;
+		hsb->part = -1;
+		hsb->session = -1;
+	}
+
+	return 0;
+}
+
+static void hfs_kill_super(struct super_block *sb)
+{
+	struct hfs_sb_info *hsb = HFS_SB(sb);
+
+	kill_block_super(sb);
+	kfree(hsb);
+}
+
+static struct file_system_type hfs_fs_type = {
+	.owner		= THIS_MODULE,
+	.name		= "hfs",
+	.kill_sb	= hfs_kill_super,
+	.fs_flags	= FS_REQUIRES_DEV,
+	.init_fs_context = hfs_init_fs_context,
+};
+MODULE_ALIAS_FS("hfs");
+
+static void hfs_init_once(void *p)
+{
+	struct hfs_inode_info *i = p;
+
+	inode_init_once(&i->vfs_inode);
+}
+
+static int __init init_hfs_fs(void)
+{
+	int err;
+
+	hfs_inode_cachep = kmem_cache_create("hfs_inode_cache",
+		sizeof(struct hfs_inode_info), 0,
+		SLAB_HWCACHE_ALIGN|SLAB_ACCOUNT, hfs_init_once);
+	if (!hfs_inode_cachep)
+		return -ENOMEM;
+	err = register_filesystem(&hfs_fs_type);
+	if (err)
+		kmem_cache_destroy(hfs_inode_cachep);
+	return err;
+}
+
+static void __exit exit_hfs_fs(void)
+{
+	unregister_filesystem(&hfs_fs_type);
+
+	/*
+	 * Make sure all delayed rcu free inodes are flushed before we
+	 * destroy cache.
+	 */
+	rcu_barrier();
+	kmem_cache_destroy(hfs_inode_cachep);
+}
+
+module_init(init_hfs_fs)
+module_exit(exit_hfs_fs)